The explosive growth of optical communications has generated the need to develop modulation and coding schemes that are robust against distortion over long transmission distances, easy to implement, and reliable. With respect to phase shift modulation alone, much work has been published regarding, for example, phase shift keying (PSK), differential phase shift keying (DPSK), and quadrature phase shift keying (QPSK), to name a few. To date, while many proposals have been made, there is still a need to improve the long haul performance of such systems.